Security is an important concern in the realm of documents and digital production and/or reproduction of the same to prevent effective printing/copying of certain documents such as high-value printed items including tickets, financial instruments, security passes, pharmaceutical prescriptions, and the like. In security applications, it is desirable to add information to a document that prevents or hinders alterations and counterfeiting. These security elements may conflict with the overall aesthetics of the document.
Watermarking is a common way to ensure security in digital documents. Many watermarking approaches exist with different trade-offs in cost, fragility, robustness, etc. One prior art approach is to use special ink rendering where the inks are invisible under standard illumination. These inks normally respond to light outside the visible range and thereby may be made visible. Examples of such extra-spectral techniques are UV (ultra-violet) and IR (infrared). Another approach taken to provide secure digital documents is digital watermarking (such as correlation marks). However, these special inks and materials are often difficult to incorporate into standard electro-photographic or other non-impact printing systems like solid ink printers, either due to cost, availability or physical/chemical properties.
Use of specialty imaging elements (e.g., GlossMark™ text, microtext lines, etc.) in watermarking to provide fraud protection and anti-counterfeiting measures allows for the use of standard paper inks and toners. While earlier specialty imaging text techniques took up space (or real estate) in the document, and also lack aesthetic value, recent methods allow for casting specialty imaging elements through a dynamic pattern generation process such that the specialty imaging elements can be used with broader design freedom with less restrictions on the use of variable data (e.g., security properties). This may be accomplished by creating a pattern color space (also referred to as “pattern ink cell”) that incorporates specialty imaging features using standard page description language (PDL) constructs, such as PostScript constructs. The pattern color space can be selected as a color for a color parameter for an object (e.g., lines, text, geometric shapes, freeform shapes, etc.) or an object characteristic (e.g., line color, fill color, foreground color, background color, etc.). In other words, within a PDL, one can implement specialty imaging text and specialty imaging pattern ink cells. Rather than defining the specific string to be rendered at a specified location on the page, a specialty imaging string may be used to define a dynamically created pattern ink cell. This pattern ink cell is subsequently accessible by other PDL drawing and rendering commands through selection as a color parameter in the command. This type of pattern ink cell is a dynamic variable pattern ink cell that adjusts its size depending on the text string used to define the pattern ink cell. UV and/or IR encoding may also be included in the specialty imaging using a pair of fixed size pattern ink cells that appear to be the same (one lets the UV or IR light pass through and other blocks it) to create the specialty imaging effect.
However, the pattern ink cells used in the above described specialty imaging require exact pixel size and placement to prevent degradation and for accurate printing. This is because while most non-specialty imaging fonts are designed to be scalable and work at a wide range of sizes so that characters that use the font can be placed anywhere on a page in any combination and/or size, specialized fonts used in pattern ink cell such as microtext, Xerox GlossMark™ fonts and Correlation Mark fonts are designed to work at exactly one size based on pixel width and height. Similarly, for a pair of pattern ink cells that may be used to create a UV and/or IR based specialty imaging effect, the size of each of the pattern ink cells is fixed irrespective of the device resolution. Hence, pattern ink cells created for one resolution (e.g., 600×600 dpi) will not work if the resolution if printed using a different resolution (e.g., 1200×1200 dots per inch (dpi)). In addition, many specialized fonts and/or images must be placed in an exact pixel position on a page and be rotated only 0, 90, 180 or 270 degrees if the resolution is square (e.g., 600×600 dpi), or only 0 or 180 degrees if the resolution is not square (e.g., 600×390 dpi). If one particular font works at a height of 240 pixels (which equals 28.8 points on a 600×600 dpi device). Hence, the specialty imaging effect fails or is distorted upon application of even the slightest bit of scaling or displacement (such as change in position or rotation), and in order to achieve a different size an entire pattern ink cell must be provided.
An example of this is shown in FIG. 1, in which a portion of a document 101 is printed by a print device with a speed setting of 325 and a resolution is 600×600 dpi. In this example, the microtext as printed is under one point in size (where one point= 1/72 inch), although it has been zoomed in FIG. 1 for purpose of illustration. Document portion 102 has been printed after the print device's speed setting was changed to 500, and the resolution was changed to 390×600 dpi. The same microtext font was used in document 101 and document 102, but the change to the print device's speed and resolution caused the font to no longer correctly work in document 102. Some of the glyphs in document 102 (such as the numbers “4” and “1” are still discernible, but others (such as “6”, “0” and “9” have been altered so that they are no longer recognizable.
However, different print devices support different or multiple hardware resolution and, therefore, for pattern ink cell based specialty imaging effects, a new pattern ink cell must be created for each hardware resolution. In other words, a device-specific pattern ink cell must be created for and/or assigned to the device. This adds complexity in creating and tracking different pattern ink cells for different devices having multiple resolutions. While certain methods exist to adjust the font size of a specialty imaging text, they work at the cost of losing the “what you see is what you get” or WYSIWIG, i.e., the document is displayed during document creation in the same way it is expected to be finally displayed or printed.
This document describes devices and methods that are intended to address issues discussed above and/or other issues.